We report a marked improvement in STM images of graphite surfaces taken in air when scanning is performed with tunneling tips which have been previously exposed to thin films of fullerenes. Spectroscopy, TEM measurements, and previous studies on the bonding of C60 to various substrates indicate that such treatment results in the adsorption of fullerene molecules on the tip. The adsorbed fullerene molecules stay attached to the tip, and once prepared are stable with respect to sample transfer. The reduced noise and enhanced corrugation of the images of graphite surfaces obtained with these fullerene-coated tips suggest that a modified Pethica mechanism may play an important role in obtaining these images.

We review the rate equation method of modeling epitaxial growth on a flat surface, where the predominant growth mode is via nucleation and growth of adatom islands. We apply a similar method to investigate the step-edge propagation growth mode on stepped (vicinal) surfaces. Unlike the intuitive picture of step-edge propagation whereby the surface morphology is invariant in a moving reference frame, results show oscillations in the step-edge positions about mean values (dependent on initial step-edge distribution). This could have important consequences in the growth of vertical superlattices. We have combined the two previous models to describe a more general case of growth, on stepped surfaces, where both nucleation through adatom islands and step-edge growth occur. Calculated reflection high-energy electron diffraction oscillations from this model will be compared with experimental results.

The intensities of several reflection high-energy electron-diffraction beams have been recorded simultaneously at varying angles of incidence and crystal substrate azimuth angles during molecular-beam-epitaxial growth of GaAs(100). Strong oscillations in the intensities of specular and nonspecular beams with the same period but varying phases have been measured. The phase of the oscillations of the various beams has been found to vary with incident and azimuthal angle. A kinematic calculation based upon a simple model for epitaxial growth is presented, and its prediction concerning phase is compared with the experimental results. The results are also examined with regard to recent studies of the role of Kikuchi processes on the phase of the specular beam.